We propose to study development using the bacterium Myxococcus xanthus as a model system. This bacterium is interesting because it has a complex life cycle involving cellular aggregation and fruiting body formation. Our specific objectives are: (a) To study the roles of three very abundant developmentally regulated proteins from M. xanthus: myxobacterial hemagglutinin, protein S, and protein S1. We plan to do this by analysis of the motility and cell-cell association patterns of mutants defective in the synthesis of these proteins, by identifying and purifying binding proteins or receptors, and by characterizing different cell types which appear during development. (b) To study the role of the frizzy (frz) genes in developmental aggregation. These genes control directional movement of M. xanthus and are expressed during development. We plan to purify and characterize the frz gene products and to sequence the frz DNA. We also plan to follow the motility and cell-cell association patterns of the frz mutants by time-lapse video microscopy and by scanning electron microscopy. (c) To study the mechanism of cellular aggregation by analysis of temperature dependent aggregation genes (tag). We plan to isolate the tag gene products and characterize them. We also plan to isolate temperature independent aggregation mutants which may be blocked in a second aggregation pathway.